The demand for mobile data and voice communication continues to evidence significant growth. Examples for mobile communication systems include cellular-based wireless communication networks. Such networks include various network nodes. The network nodes may include base stations which respectively provide coverage for a radio cell.
A user equipment of a mobile communication network may be a Proximity Service (ProSe) enabled device. Several ProSe enabled user equipments which are located in proximity to each other are operative to perform device-to-device (D2D) communication. D2D communication allows user equipments of a mobile communication network to directly communicate with each other when the user equipments are located in proximity to each other. D2D communication has a wide variety of applications, including public safety and other use cases. Emergency calls are one example for public safety use cases of D2D communication. For illustration, if a user equipment indicates an emergency call situation, another user equipment may provide repeater function to ensure good network coverage for the user equipment. Direct data or voice communication between user equipments is another example for use cases of D2D communication. For illustration, ProSe enabled user equipments located in proximity to each other may engage in data or voice communication. The respective D2D communication is not transmitted to the radio access network of the mobile communication network.
In order to perform D2D communication, a user equipment must be capable of detecting one or several other user equipments which are located in proximity to the user equipment. The resources, e.g. the subcarrier frequencies, slots and/or symbols which the user equipment may use for the device-to-device discovery may be allocated to the user equipment by a base station. When different user equipments are located in proximity to each other, but are under the control of different base stations, they may use different resources for performing the device-to-device discovery and/or device-to-device communication. It is desirable that user equipments located in proximity to each other can reliably perform device-to-device discovery and/or device-to-device communication even when different device-to-device resources may be allocated to them. This may happen when the user equipments are controlled by different cells or are even attached to different public land mobile networks (PLMNs).